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Tabbie

Mycoplasma pneumoniae

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Hi All

Hypothetical Senario

Female patient unknown transfusion history with mycoplasma pneumoniae what exclusions and further testing would you perform ? 

When would you perform a titre ? Reactions greater than 3+. If emergency units required with titre greater than 64 what is your protocol ?

Thanks

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Presuming you are in a normal lab, you should

1.  Find out about transfusion history as a matter of considerable urgency, including plasma products

2.  do your normal exclusions  (I would be a bit worried about an anti-Jkb with something else

3.  Use additional cells

4.  Put up a saline RT panel

5.  Fully phenotype your patient

6.  Do a DAT - look very hard for a mixed field

Then review!

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Great thanks Galvania

More questions :) 

If it was an anti-I would the pattern be pan-reactive by IAT weaker and Enzyme stronger reactions?

If patient was previously transfused would you phenotype RBC if you knew the group of the ABO mismatch i.e. if a dual population say Group A given to a group O? Would you perform an eluate to remove the antibodies then add anti-A to remove the A RBC then phenotype the O RBC and assume they are the patients RBC as the phenotype?

If you only knew that the patient had been transfused but no other details how would you phenotype or would you just obtain a genotype?

If no mix field and DAT C3d only and Donath Landsteiner test was positive would you then titer with P antigen positive RBC?

Cheers  

 

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1 hour ago, Tabbie said:

If no mix field and DAT C3d only and Donath Landsteiner test was positive would you then titer with P antigen positive RBC?

 

NO!  Under no circumstances, even if the DAT was negative with anti-C3d (as it usually is in cases of PCH).  The titre (Tabbie, you are in the UK, so spell it the correct UK way!  :D:D:D:D:D) is of no relevance whatsoever, and knowing it would make no difference to the way the patient is treated.

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I work in a small lab we just don't get the experience of the unusual. I am trying to learn more by posting hypothetical case studies as I cant post real ones.

Thanks

 

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So for example the question below

If you only knew that the patient had been transfused but no other details how would you phenotype or would you just obtain a genotype?

The BSH guidelines say " If the patient is known to have been transfused in the previous three months, phenotyping may be misleading"

Most regularly transfused patients such as Haemoglobinopathy patients  admittedly would already be phenotyped but if they were not they would required Rh K matching units, DARA patients would you Rh phenotype if units are required ASAP but you have time for a crossmatch.

What further tests would you do if you had the resources to ensure you provided matched units

So for example after the elution to identify the antibodies can you use the RBC left from the process to phenotype ? or does the elution damaged the RBC is there another procedure for phenotyping if the patient has been recently transfused?  

Misleading means ? - What anomalies would you actually see ? weakened reactions, dual populations (if ABO) anything else?

Why with warm autoantibodies does elution not help ? What about in pregnancy are there any anomalies with elution/adsorption/phenotyping ?

Thanks
 

 

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Phew!  There are a few questions there!

Most haemoglobinopathy patients within the area covered by NHSBT would have been genotyped during the time when this was undertaken gratis by the NHSBT.  As far as I know, with a results being hidden from view by ill-informed Caldicott guardians, who seem not to understand their role, most of these results are open to view on Sp-ICE.  Those that are not available on Sp-ICE (either because of the rogue Caldicott guardians, or because the patient themselves decided not to take up the offer of a free genotype) can still have their genotype performed, but it will now cost!  This can be done whether or not the patient has been transfused (although the patient would have to agree to this and the hospital would have to pay).  If the patient has not been transfused within the previous three months (and/or has not been pregnant), then, of course, a serological phenotype can be undertaken.  Special measures apply for any patient who has received a transplant.

In the case of DARA patients, again, with the caveat concerning transfusions, pregnancy, etc, there is no reason why red cells treated with dithiothreitol (DTT) should not be used.  However, caution should be applied, because it is not just the antigens within the Kell Blood Group System that are denatured by DTT, and a quick examination of the final few pages of Reid ME, Lomas-Francis C, Olsson ML.  The Blood Group Antigen FactsBook.  3rd edition, 2012, Academic Press will reveal the list of those other antigen affected.

Other tests would, of course, include testing for underlying clinically significant atypical antibodies with DTT-treated antibody screening red cells, and, if necessary, DTT-treated antibody identification red cells.  BSH Guidelines recommend that K Negative red cells are given, unless the patient is known to be K+k-, when K- blood should be given (if available).

Almost all elution techniques available damage red cells beyond any chance of being able to phenotype them after the antibody has been removed, whereas those sufficiently gentle to leave viable red cells are ineffective in removing all antibodies from the red cell surface.  Therefore, once again, I would suggest that a genotype is the way to go (incidentally, I should caution here, and should really have cautioned above, that a genotype, however good, is only a prediction of the phenotype of the red cells, even if the patient has never been transfused and never been pregnant - it is not a panacea).

ALL results that are not absolutely and utterly cut and dried (no weak reactions detected, no mixed-field reactions detected, etc) can be misleading, unless the background to these anomalous reactions are known for certain, otherwise it is GUESSING, and there is never an excuse for guessing in blood transfusion (even making an informed hypothesis, without going on to prove the hypothesis, can lead to fatalities).

Elution seldom helps in cases of WAIHA, because the antibody causing the AIHA will almost always be panagglutinins, and so the eluate will react with all red cells tested (with a few exceptions when incredibly rare red cells can be shown to be negative, such as Rhnull red cells or Wr(a+b-) red cells, and no serologist in their right mind would waste such cells, unless there is a very good reason to use them, when, of course, they are not being wasted!).  Because of this, it is rare in the extreme to be able to detect alloantibodies in an eluate under such circumstances (unless the eluate itself is alloadsorbed, but then, why not perform alloadsorption on the plasma, as there is usually more of this available?

I hope this helps!  I've answered most of your points, but, I appreciate, not all (my typing fingers are beginning to ache!), but, if you need more help, I will try.

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And going back to the first case.  Were those results 'made up' or did you actually have a patient that gave those results?

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Thanks Galvania

All made up so if you don't ever see something I have 'made up' please let me know. I was trying to fit lots of questions into one scenario.

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On 7/21/2018 at 3:40 AM, Tabbie said:

Hi All

Hypothetical Senario

Female patient unknown transfusion history with mycoplasma pneumoniae what exclusions and further testing would you perform ? 

When would you perform a titre ? Reactions greater than 3+. If emergency units required with titre greater than 64 what is your protocol ?

Thanks

image.jpg

I love made up cases!!!  Do we get more information in this case after we answer your questions? Anyhow, here are my thoughts. 

"Female patient unknown transfusion history" I would perform antigen typing for D,C,E,c,e,K,S,s,Fya,Fyb, Jka and Jkb antigens and see if I detect mixed field reactions. 

"with mycoplasma pneumoniae"  I would like to see the results of direct agglutination test (immediate spin or room temperature) based on this diagnostics using Group O adult cells and cord cells. This antigram only includes IAT where anti-I may not be demonstrable. 

"which  what exclusions and further testing would you perform"  I would also like to see the DAT and Eluate from the cells (especially if I see mixed field reactions in my antigen typing) 

"When would you perform a titre ?" If the reaction with Group O adult and cord were both positive (tested at room temperature direct agglutination phase), I would perform titer using Group O adult and Cord cells in parallel to confirm the specificity of reaction seen in room temperature.  Reactions greater than 3+.

 "If emergency units required with titre greater than 64 what is your protocol ?" I would make sure that transfusion is absolutely necessary by involving medical staffs.

Lastly, I would like to perform ABO/Rh typing, obtain hematology test results (H/H, retic count, any abnormal RBC morphology?), Chemistry results ( Direct/Indirect Bilirubin, Heptoglobin), transfusion history (getting a list of hospitals that the patient has been to and calling each hospital has helped me alot in the past to get this information) on this patient, as it is an essential information in all cases of immunohematology investigation. Also, Drug-induced AIHA maybe a far fetch without further information, but something to be included in the back of my mind. 

 

Edited by dothandar

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